High-Resolving-Power, Ultrafast Streaked X-Ray Spectroscopy on OMEGA EP

Transcription

1 High-Resolving-Power, Ultrafast Streaked X-Ray Spectroscopy on OMEGA EP Channel 1 Crystal chamber X-ray streak camera Chamber wall Re-entrant tube with collimators Normalized signal Pulse duration: 10 ps 500 # 500 # 20-nm Cu; 400 J 250 # 250 # 10-nm Cu; 650 J 250 # 250 # 2-nm Cu; 650 J Channel 2 X-ray CCD P. M. Nilson University of Rochester Laboratory for Laser Energetics 1.65 m th Annual Meeting of the American Physical Society Division of Plasma Physics San Jose, CA 31 October 4 November

2 Summary A high-resolving-power, streaked x-ray spectrometer is being developed and tested on OMEGA EP The goal is to achieve a resolving power of several thousand and 2-ps temporal resolution (February 2017) To understand system performance, a time-integrating survey spectrometer has been deployed on OMEGA EP Survey spectrometer measurements and offline testing show focusing fidelity: ~50-nm line focus resolving power: >2000 throughput: ~10 7 ph/ph shielding: 5 to 15 cm of lead These measurements provide a firm foundation for designing and implementing the time-resolved instrument The instrument will ultimately be used to measure temperature equilibration dynamics and material response to ultrafast heating. E25274c 2

3 Collaborators F. Ehrne, C. Mileham, D. Mastrosimone, R. K. Jungquist, C. Taylor, R. Boni, J. Hassett, C. R. Stillman, S. T. Ivancic, D. J. Lonobile, R. W. Kidder, M. J. Shoup III, A. A. Solodov, C. Stoeckl, and D. H. Froula* University of Rochester Laboratory for Laser Energetics *also Department of Physics K. W. Hill, L. Gao, M. Bitter, and P. Efthimion Princeton Plasma Physics Laboratory D. D. Meyerhofer Los Alamos National Laboratory 3

4 Isochoric heating Motivation A high-energy ultrafast laser can heat solid-density material on a time scale much faster than the material expands Heating at high density produces exotic states of matter in extreme thermodynamic conditions 1 The possible extremes in temperature enables novel material and radiative properties experiments 2 E21173f e.g., mean opacity of solar interior matter 3 New diagnostic techniques are sought for testing plasma-dependent atomic processes 4 plasma opacity 5 equation-of-state models 6 These studies require dense, high-temperature plasmas that are well characterized. Temperature (ev) 10,000 1, Classic plasma Dense plasma 10 2 P ~ Gbar Conditions deep in a star C = 1 Degenerate Density (g/cm 3 ) Cores of large planets Quantum degenerate hot matter A Report on the SAUUL Workshop, Washington, DC (17 19 June 2002). 2 K. Nazir et al., Appl. Phys. Lett. 69, 3686 (1996). 3 J. E. Bailey et al., Nature 517, 56 (2015). 4 D. J. Hoarty et al., Phys. Rev. Lett. 110, (2013). 5 R. A. London and J. I. Castor, High Energy Density Phys. 9, 725 (2013). 6 M. E. Foord, D. B. Reisman, and P. T. Springer, Rev. Sci. Instrum. 75, 2586 (2004). 4

5 Motivation Outer-shell ionization affects the energy and shape of the characteristic K a line in a partially ionized plasma Hot electrons create K-shell vacancies when colliding with ions Ionization by thermal electrons removes electrons from the ions outer shells As the ionization progresses, the,2 lines increase their energy 1 5 L 3 (2p 3/2 ) L 2 (2p 1/2 ) L 1 (2s) Fine structure of the characteristic K a line Signal MTW laser: W/cm 2 Target: Cu foil nm nm E18508d K (1s) Time-resolving the K a line shift allows for the mean ionization state of the plasma to be inferred during the rapid heating phase K. Słabkowska et al., High Energy Density Phys. 15, 8 (2015). 2 K. Słabkowska et al., High Energy Density Phys. 14, 30 (2015). 3 G. Gregori et al., Contrib. Plasma Physics 45, 284 (2005). 4 P. M. Nilson et al., Phys. Plasmas 18, (2011). 5 J. F. Seely et al., High Energy Density Phys. 9, 354 (2013). 5

6 Conceptual Design The instrument is based on two diagnostic channels, each with a spherical Bragg crystal E23446b Channel 1 Si220 spherical crystal X-ray streak camera Channel 2 Si220 spherical crystal X-ray chargedcoupled device (CCD) 2.2 m 2.2 m Source Source Parameter Requirements X-ray source size ~100 nm 2 Spectral range 7.97 to 8.11 kev Crystal and Bragg angle Si220 crystal Bragg angle = 22.8 Crystal radius of curvature Crystal size Source-to-crystal distance Resolving power Spectral shifts Streak-camera slit Temporal resolution 330 mm 25 mm 100 mm 2.2 m ~5000 streak-camera limited Few ev to 20-eV K a line shifts 6-mm-long, 400-nm-wide 50-nm-high-throughput region 2 ps 6

7 Spectrometer Measurements High-power experiments show the focusing fidelity, resolving power, and throughput meet the desired requirements Energy Pixels Raw data Pixels 1200 Shot J, 1 ps Si220 Filtered data Pixels Signal ( 10 4 ADU s) The measured throughput is ph/ph The predicted peak signal at the streak camera is ~1000 ADU per pixel Photometric estimates are based on laser energy: 100 J x-ray flash duration: 10 ps Shifted spectra are well-matched to the length of the streak-camera slit Imaging Imaging Phase I has provided the foundation for designing and implementing the time-resolved instrument. E25096b 7

8 Spectrometer Measurements Time-integrated measurements on OMEGA EP show spectral shifts increasing with target energy density Pulse duration: 1 ps Pulse duration: 10 ps Normalized signal # 500 # 20-nm Cu; 100 J 250 # 250 # 10-nm Cu; 400 J 250 # 250 # 2-nm Cu; 500 J 500 # 500 # 20-nm Cu; 400 J 250 # 250 # 10-nm Cu; 650 J 250 # 250 # 2-nm Cu; 650 J E25203c 8

9 Summary/Conclusions A high-resolving-power, streaked x-ray spectrometer is being developed and tested on OMEGA EP The goal is to achieve a resolving power of several thousand and 2-ps temporal resolution (February 2017) To understand system performance, a time-integrating survey spectrometer has been deployed on OMEGA EP Survey spectrometer measurements and offline testing show focusing fidelity: ~50-nm line focus resolving power: >2000 throughput: ~10 7 ph/ph shielding: 5 to 15 cm of lead These measurements provide a firm foundation for designing and implementing the time-resolved instrument The instrument will ultimately be used to measure temperature equilibration dynamics and material response to ultrafast heating. E25274c 9

10 Model Predictions Temporal spectral shifts on the Cu K a line in rapidly heated solid matter will validate the spectrometer performance Synthetic spectra from hot, dense matter are required LSP 1 calculates E25130a energy-transport physics electromagnetic-field generation target heating LSP is post-processed based on tabulated PrismSPECT 2 calculations using the local density and temperature at the time of emission line-of-sight and high-t e opacity effects The calculations use an occupation probability model 3 and the ionization potential depression formalism of More 4 Time (ps) Time (ps) OMEGA EP 20-nm Cu foil 100 J, 1 ps OMEGA EP 10-nm Cu foil 400 J, 1 ps Normalized signal OMEGA EP 20-nm Cu foil 100 J, 1 ps OMEGA EP 10-nm Cu foil 400 J, 1 ps 1 D. R. Welch et al., Phys. Plasmas 13, (2006). 2 Prism Computational Sciences Inc., Madison, WI D. G. Hummer and D. Mihalas, Astrophys. J. 331, 794 (1988). 4 R. M. More, J. Quant. Spectrosc. Radiat. Transf. 27, 345 (1982). 10